Fluorosurfactants are useful to provide surface effects, for example wetting, lowering surface tension, leveling, and foaming, in various applications such as coatings, floor finishes, cleaners, acid etching applications and oil field applications. Many commercially available surfactants contain perfluoroalkyl terminal chains. It is known in the art that as the length of fluorinated alkyl chains decrease, the performance characteristics of surface properties imparted to substrates treated therewith decrease as well. See Honda, et al., in “Molecular Aggregation Structure and Surface Properties of Poly(fluoroalkylacrylate) Thin Films” Macromolecules (2005), 38(13), 5699-5705. Honda et al. disclose that a perfluoroalkyl chain of at least 8 carbons is necessary to maintain the perfluoroalkyl chains in a parallel orientation. Shortening of the perfluoroalkyl chain, causes reorientation which results in a loss of performance.
Common fluorosurfactants are prepared through a fluorinated sulfonyl chloride intermediate. These intermediates are costly to produce and are in limited supply. Some preparations require a conversion of a fluorinated SCN moiety to a fluorinated SO2Cl moiety, which involves a reaction with gaseous chlorine, a very hazardous material. It is desirable to eliminate this reaction.
U.S. Pat. No. 4,383,929 discloses fluorinated sulphonobetaine compounds prepared from amines derived from fluorinated sulfonyl chloride intermediates. U.S. Pat. No. 6,201,122 discloses a fluoroaliphatic radical-containing sulfonamido anionic compound. These compounds are useful as anionic surfactants in liquids and are prepared through fluorinated sulfonyl chloride intermediates.
Additionally, precipitation is a known problem associated with anionic surfactants in some end use applications, such as oilfield applications. Precipitation causes degradation or complete loss of performance thus needs to be avoided.
It is desirable to have fluorosurfactant compounds with improved properties that can be produced from readily available fluorinated amines and alcohols without the need to use gaseous chlorine. Also desired is a method of altering the surface behaviors of liquids using these fluorosurfactant compounds which avoid precipitation problems. The present invention provides such compounds and methods.